1985 300D shifting hard only when AC on
 

Seems I have a vacuum issue that is very specific and am wondering if anyone ran into the same issue before and what the leak was before I go all basic vac system troubleshooting.


My 300D shifts up and down pretty hard but only with the AC on. When off, or EC it shifts fine and smooth. Was there a specific module that was the culprit for you if you had this issue? Ideas where to start?


Thanks!

Check vacuum pods for leaks. The recirculation pod may be bad, if so, when it engages during A/C usage you have a relatively large vacuum leak.

Welcome to the site as well. Since you are probably new here with your first post. You may or may not know the transmission is very vacuum dependant on these transmissions.

Keenly aware of that now... my vac hose to my modulator was dislodged when I changed the oil filter... Trans shifted like manual valve body air shifter lol.


I'm thinking this has to be in the climate vac distribution module. The vac leak is present in any of the modes except off and economy.

Where's that one at? I'll definitely test it! Thanks.

The subject of 123.xyz vacuum elements has been discussed in this forum for many years and ad nauseam. A search of the archives will yield much detailed information. Best of luck to you with this.

Most likely the center pod.

Check your vacuum level too...I once had a vacuum pump that was marginal on my 300D and any demand on vacuum caused a transient shift event...replaced vacuum pump with a rebuild and it was great...good luck...